Trunking arrangement for automatic telephone-exchanges.



T A. G. MARTlN. IRuNKlNG ARRANGEMENT FOR AUTOMATIC TELEPHONE EXCHANGES.

APPLICATION FILED )ULY 23.1906.

Patented Apr. 4, 1916.

2 SHEETS-SHEET l.

AWM Ul Ufa??? @gif/@5f if@ M @deyj T. G. MARTIN.

TRUNKING ARRANGEMENY Fon AUTOMATIC TELEPHONE EXCHANGES.

APPLICATION FILED JULY 23.1906,

Patented Apr. i, 1916.

Z SHEETS-SHUI 2.

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TAILBCT G. MARTIN, $1' CHICA 3, Il.

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GenerabA .stated the object of my uve/lr tion is the prem, on im improv@ and highly efxcsm telephone Xchange System.

Spefia objects are the provisin ff :m improved arrangement for antumaticay trunking between different exchanges or central Stations; the prm'siun of .mprwzed means whereby the mlingj subswber may employ mi@ m' more relays fm* ucceswly controlngff a pim-dit? cf automat@ e t Such, fm' example, u seonnd-fsucr0r and a connector; tha {')rfwson o' i repeater hun"A ing; n pair of ffv'cxssea limi 1^ z-::w r-1 having u pair of inductive relay minis through which current', fur lking; purl" is supplied tw me cn'nggj snfswrw and by whim Hw czd a subfcrhr coma a Selector or connector 0r uti* ,Y machine over a trunk Une fzfuing thereto and formed hy a contuwnfm ai" th@ Suid, crossed conucwrs; the mfv v mon battery tlrpmm for inistlrng ugauvvs u'flvef'ini; on the )mrt of' a www other switch: Y :midi

(im i arfu w11 ai: Erickson..

switch wi ers 15, 16, 19 contact points 17, 18, 22 and 23, respectively.

,30 therefore, the side 50 nection 4liti energized The ysubscribers vertical and rotary lineQconductors 11 and 12, respectivel termlnate in the vertical and rotary line relays 13 and y 14, the connection being maintained through ,5 the side switch wipers 15 and 16. The former wiper is normally in en agement with rthe contact point 17 and the contact point 18. The .side switch vis well known, and comprises besides the side swltch 0 wipers 15 and 16 the private side switch wiper 19 and the rotary-magnet side switch wiper 20. The side switch 1s controlled by the`- private magnet 21, and in the normal or first position of the side switch the slde and 20 engage the In second position they rest on the Contact 'points 24, 25, 26 and 27. In third position they engage the contact points 28, 29, and

20 31, lrespectively. Through .the medium of the vertical line relay 13, and while the side switch is infirst osition, the subscriber controls the vertica magnet 32 which operates vertically the switch-shaft (not shown) that 25 carries the line wilers 33 and 34 and the private wiper 35.

hrough the medium of the rotary line relay 14,y and while the side switch is in first or second position, the subscriber controls the private magnet 21 and, switch. When the side switch is'in second position the rotary magnet 36 is energized and the switch-shaft that carries the wipers 33, 34 and 35 is operated `in a rotary direction. l The vertical and ro .35, tary lin' relays 13 and 14 provide the means by which the release I'magnet 37 is controlled by the subscriber while the side switch 1s /rst or, second position. If the side switch `passes to thlrd osition, however,

4,0 sincethe selector` B is o, the trunk release type, the selector is coxrtrolled through the v next switch withA which/a connection has been established, and through the private wiper 35 by means of the backease-relay 35. The switcleshaft of the se ector B carries a so-called normal post arm 38 which, when the shaft is in normal position, presses the spring 39 intoengagement with the contact point 40, and thereby maintains a conetween the bri ge-cut-of-relay 41 and ythe private .normal conductor 42 that leads to the connector private bank. By way of the said private normal conductor, furthermore, the bridge-cutolfrelay 41 is whenever an;7 subscriber calls the substation A. The bridgecuto`:tl-relay controls a connection between the vertical and rotary line relays 13 and 14 and between the said relays and battery B. It is desirable to disconnect therelays from each other and from the battery because if not the ringing current for signaling the substation A may operate either or both of the relays 13 and 14 and cause fsome interference with the connection.` It is also deatter with the sirable, as is well known, to remove the bridge formed through the said line relays 14 and 13v from across the line' to give the Avoice-currents as clear a path as possible.

enever the selector-switch B is operated, however, the spring 39 engages the ground contact 43 justn above it and thus grounds the private normal conductor 42 and the private bank contacts at the connector banks corresponding to the number of the substation A, so that no calling subscriber .may be able to call in upon substation As line after a calling operation has once been started from that station.

The repeater C of my invention has no movable parts such as the shaft and side vswitch in the selector, but is made up number of relays and springs and other de tails as follows: The instrument is designed to be bridged permanently across a trunk line, or other l1ne, in the same vmannergas the repeater C is shown bridged across a trunk line that connects the exchange #l with exchange #n The said repeater is provided with a vertical line relay 44, a rotary line relay 45, a dierential relay A46, a pole changing relay 47, a resistance-coil 48 and a couple of condensers 49 and 50. The line relays 44 and'45 control between them the trunk release The differential relay with two windings 64 and wound that 46 is provided 65 which are so if current is sent through them relay 46 wil not magnetize. The oilice of this relay is to provide means whereby the calling subscriber may be able to release after a called subscriber has answered.

urthermore, the differential relay, being provided with the sprin 66 and contact point 67, prevents impu ses that are repeated from the subscribers line conductor 11 to the vertical trunk conductor 62 from passing to the rotarytrunk conductor 63; and it also prevents impulses repeated from the subscribers rotary line conductor 12 to the rotary trunk conductor 63 from passing to the vertical trunk conductor 62.

The second-selector G is the same as the first-selector B with the exception that there are no normal conductors like. the normal conductors 68 and 69 leading to the con neetor banks7 There is also no use in the second-selector for euch a relay the Abridge-CUt-oil-relay 4l of the iret-seleet0r l5 and it is, therefore. omitted. The. vertianl and rotary line relays 70 und Tl. are there fore connected directly to battery B2. There is also no necessity for n private normal. conductor such as the -privzie normal Conduetor 42. and the spring T2 controlled by the normal post arm T3 le Connected tlm-ol l1 rin off-normal lomp Tel. which lutter liet-om f' lighted when the said epring 1:5 engages the grounded Contact point 75, thus indicating to the switchboard attendant when 'the selector is ofi' normal. Since like parte are likewise represented throughout the drain ings, the vertical magnet 76, the releasemagnet 77, rotary magnet 7S, private magnet 79 and the back-releuse-relay 8O will be recognized and understood.

The connector-switch F may also be of :my suitable or approved type. for instanee of the general type described in Patent No. 815.17?, granted March 1?, i906, to Keith, Erickson & Erickson. The mechanical deu tails of the selector and Connector, as is well known7 are very much the saine, although there is some material diiference in the eircuits. For instance, the connector' switch shaft, which is not shown. carries, like the Selectors, the line wipers 81 and S2 and the private wiper 83.- The connector Switch is also controlled by the calling subscriber through'the mediinn of the vertical und rn'- tary line relays 84 find. The vertical line relay Si directly controls the vertical ningnet 86 and also the rotary magnet 87. The

(illico of the said magnet 8G is to give the shaft and shaft Wipers. their vertical movemente. and the rotary magnet Si' imparte to the said shaft -ind wipers e. rotary or sirenlar movement. The rotary line relay controls the private magnet 85, which hitter under vermin conditions: Controls in turn the vertical and rotary mognets 8G nml ST. the 1eleasenii2net 89 and :also the side switch wipers 9U, 91. 92! and fill. The said. side switch, like the eide en'iteh oi the selefftor. ling :i nornnil or .tiret .foeitioii. i eeeoiid sind a third position. ln the, normal ponition Alle respective side :Switch wipers 4), ill, 12 and JB engage tho Contact points lll, llo, 96 and 97; in second position the Wipers engage the Contact points Q8. ill?, 1GO rind lOl; sind in third position they engage the Contact points 10Q, 103 104 .-fi. d 105. The relr-esr.A nmgnet Si! ie also eontrolled by the line re lays S4 und oonjointly. and by the circuit controlling relay '106. Like the repeater the connector divides the circuit that passes through it into two sections by the use of the Condensers i025 und M9. The vennoot-or hue in addition, :i ringer relay .l it ily means of ivliirh the ringer generator ill is. bridged im 5;: the terminals iii" the celle-ii line lo .Qignol the felled inheeriier. Each exchange has n busy ggnaling apparatus H of any @nimble design., ro. for example the one uw prieing :in inlernpter 1li! in eeriezrl with n primary winding i155 of :in indnetion'roii lll ln-roby n 'buey signaling enrrerl if. induced intr the a Hillary Winiilin;r of the sind in(mation-coil lli, The l l winding;r lli le ronneeted to the Contact wint lli? iigainai nhiih the? .inviti-li :luft spring; il? i allowed to prf s when the rim"- mlil preterm iltl rises.

The first'selector lil olf the exiled line ie the 'rianne :is the iiet-selertoi B sind needn, therefore. no description. The substation l) is. ol' conte. oleo the some a@ the Salir station A.

The connection between the two exchanges may he arranged in any Convenient man ner, and l do not confine myself to any particular nrrsinfenient, Since the System herein disclosed admits of :in indefinite number ol nrrzmgoments, Ii it is assumed that the maximum number oi. snlsrrilieixi to he lieeommodlited zit each of the changes #l and #2 is live thousand. then the first live levels of the lirst-seleetorn of exchange #l muy be devoted to local con nertions and the lust five levels to trunk. Connections for exchange #2; each of which trunk eonneetions, of course, comprises :i repeater similar to the repeater (l. .M the exchange #il :i similar nrrangrenient may prevail. hot with the exception that the iirst live levels would lie devoted 'to trnnliing appamtne :it 'the oXohlinge :rnd the inrit five levels to local connections. lion-eier.y un;Y suitable armi" fluent .rn-(1v be i"`\*.,i,e i to. lt will lie uwV VStood that the switches may he Irrsinn l in groups; 'for enziinple. tio iirebselectors muy be arranged in groups oi. one hundred having all similar hunk conferite ronneeled in mnltiple.' There fore. there, will lie one hundred line terminals in multiplo with r-:irli trunk line. end

suitable manner eorresponding 'Lo euch digit. For envi; d' the vertical liml ie grounded :i vermin number of timex corre sprmilingr to the numerical wine of the de". l'llin the rotfii'y side of the line is grounded once. The Iii-et digit being' i ila snliserilier at Slilwnilion A remorof his; ro

ceiver from the ewitelrliook whirh hitter then causes the ground springs 115) and l2() to clone Contact. the` eeronilmv renvoit springe ll :vi/m1 i214 contrari. Springs 17" uw. ,lill rai-aise eimlriet. :dni the.

Cloer' img I battery B1 to ground G1.

wwwwmmwwwm switchhook breaks connection with the spring 125, and the calling subscriber then post 126 in connection ground G3. button 8 is pressed the spring 127 leaves the contact point 128 and 10 is grounded on the ground post 126, and as a result the vertical line relay 13 of the selector B is energized once. The current for energizing said relay 13 Hows from ground h the ground springs 119 and 120 to the ground post 126, thence tothe vertical line conductor 11, side switchwiper 15, cor act point 17, vertical line frelay 13, bridge-cutoi'relay springs 129 and 130 to the battery lead 131, thence through battery Bl to ground G1. Each time that the vertical line relay 13 is energized the line relay springs 132 and 133 are pressed into contact and an energizing circuit is thereby established each time through the vertical magnet 32.l Current orsaid magnet flows fromground G4 through the springs 133 and 132, private springs 134 and 135, vertical magnet 32 to the battery lead 131, thence through battery B1 to ground G. 30 The vertical magnet 32 then operates to raise the shaft two steps, thus placing the wipers 33, 34 and 35 on a level with the contact points that constitute the terminals of the trunk line leading to thef'repeater C.

a5 The subscriber then presses the rotary button 9, causing the spring 136 to leave the contact point 137 and to be grounded on theground post 126. As a result the rotary line conductor 12 is grounded and the rotary line relay 14 is in turn energ'zed. The current through the Said relay 14 flows rom ground G3 to the ground post 126,

rotary line relay springs 138, 129 and 130, thence through battery B1 to ground G1. The rotary .line relay 14 in turn energizes the private rnagnet 21 by closing connection between the springs 133 and 139.

he current for energizing magnet flows from ground G* springs 133 and 139 to the 21, and through battery Bl The private magnet 2l then lease the side switch from sition, and as a result a circuit is closed through the rotary magnet 36 when the side switch wiper 20 engages the contact point 27. The current through the rotary magnet flows from ground G5 to the Contact point 27, thence through the side switch wiper 20, rotary magnet 36, rotary magnet interrupter springs, to the battery lead 131 and throughV The rotary magthe private through the private magnet to ground G1. operates to refirst to second po- Therefore,

net is energized one .step and the wipers 33, 34 and 35 carried into engagement with the bank contacts that constitute the terminals of trunk lines.` If the first trunk line is busy an energizing circuit is established through the private magnet 21 when the private wiper 35 strikes a grounded contact. The current flows, in that case, from. ground to the private wiper 35, thence through the back-releaserelay 35', side switch wiper 19, contact point 26, private magnet to the battery lead 131, thnce through battery B3 to ground G1. As long "fa the priva te wiper 35 passes over the busy im 'act point the priu vate magnet 21 is retained ein gleed and the side switch is locked in ud position, as is well known, energizing step past the last bus soon as the by stop, emr" i up :.f. f trunk line, .ly/lowcuer. as private magnet dciiergizes, the side Switch is tripped into third posi l if there are no busy contacts t be passed over, the rotary magnet 33. as is f* l known, trips the side switch to third position with the result that as soon the side switch wipers 15 and 16 engage the respective oontact points 28 and 29 the subscribers line conductors 11 and 12 are extended to the repeater C. Also, since the de switch wiper 19 at the same time engages the grounded Contact point 31), a guarding potential tablished at the private Wiper 35 for prfucct-v ing the seized trunk line tu the repeater *C from being u'iolested hy any other Snitch.. The second digit being 2 the calling suhscriber presses the button 3 twice and. grounds the vertical line conductor l l twice. Grounding the vertical line conductor twice energizes the vertical vline relaj` H tu The energizing current in each cese lows from ground G3 at the substation to the ground post 126, thence through thc 'i 12T to the vertical line conductor 11. e switch wiper lo, contact point f, veiti ai line Wiper 33, vor ...cui line relay ll peuter C. Winding cil oi" thc diifrcntial relay 46, gole changing relay springs 60 and to the battery lead 13E, thence through hat tery B to ground Gi. Since the current flows not only through the vertical line relay #14 but also through the winding 61 of the differential relay 46, the di ffereutial relay energizes simultaneousiy 'with the said verticclline relay. Each time that the von tical line relay is energized the springs .33 and 55 are pressed into contact. each time grounding the Vertical trunk conductor 5i? over the following circuit; from ground d through the pole changing relay springs and` 58, conductor 143, conductor 11.11. polo changing rela;7 sprl 57 and 56 tc the 'tei-tical, trunk conductor t.

he effect of groum ng 'this vertical iii-unl: conductor will be explained hereinafter. When the differential relay 46 `hecornes ensprings 55 and L Haat th u; T con 'Y Eine 17e wlmiing' L, -i w Hw, mfmy B1 i@ I rrr.

Hush Mme limi: New wam' um #a ihr: qll-'w ml mamut s: f Mam-imm? 533 is wim' operating the kif-rings Si? fs-funding! of the wz 6i! l `rough om@ ills Sonor d M4 to Suid verticu magnet T6 is es throufr Hw. u

Lil) and, 150 a? gage this grounded Contact point a5 und the wif-nmma amp 74 flushes up to mlwsi th@ !f thv @minding mf the midi wipers of windings 163 an selector G (Fig. 2)

2o through battery B to trolling relay springs 1 G F and differential second-selector 145 and thro 11 is grounded the vertical line relay 44 of the repeater C is energized, as well as the differential relay 46, over a well-known circuit. 'The vertical line relay 44 in turn 5 grounds the vertical trunk conductor 62 twice, and as a result the vertical line relay e di 84 of the connector F` together with th ferential relay 162 are energized. The said differential relay is rovided with a couple 164., The circuit or energizing said relays 84 and 162 extends from ground G at the repeater C (Fig. 1) to the vertical trunk conductor 62, thence tothe side switch wiper 143 of the secondcontact point 158, vertical line wiper 146, vertical line relay 84, winding 163 of thev differential relay 162, through the pole changing relay springs 165 andv 166 to the battery lead 145, hence ground G3. The vertical line relay 84 in turn presses the line relay springs 167 and 168into contact and as a result the vertical magnet 86 is operated. The current through the said verti- 25 cal magnet flows from ground Gr9 through the springs 168 and 167, yprivate springs 1 69 and 170, side switch wiper 93, contact point 97 to the vertical magnet 86, thence through saidv magnet and throu h.the circuit-con,- 1, 172 and 173 to the battery lead 145, thence through battery B2 to ground G2. The vertical -in agnet 86, as usual, operates to raise the switch-shaft and the wipers 81, 82 yand 83. The vertical y 85 magnet being operated twice the connectorshaft is raised two steps and the said wipers 81, 82 and 83 are carrled )to a level 1n which the line terminal of the subscriber #2220 1s located. The energization of the differ- 40 ential relay 162 has no significance at this time. After operating the vertical button 8 with the above result the subscriber then presses the rotary button 9 once, grounds the rotary line conductor 12, and as a re 45 sult operates the rotary line relay 45 of the repeater C (Fig. 1), together with the difv-ferential relay 46. As a result the rotary trunk conductor 63' is grounded once and the rotary line relay 85 of the conductor relay 162 are energized. The current through said relays 85 and 162 flows from ground G at the repeater C (Fig. 1) to the rotary trunk conductor 63, thence to the side vswitch wiper 153 of the `G (Fig. 2) to the contact point 159 and rotary line wiper 147. t o the rotary line relay 85, thence through'sald relay and through the winding 164 of the diierential h `battery B2 to ground G2. The rotary l erelay 85 upon energizm presses the line relay springs 174 and 168 into: contact, establishing, therefore, an energizin circuit through the private mag net 88. he current through Asaid magnet relay' 162 to the battery leady marked by the heavy lines in tary magnet 87 for the vertical magnet 86 to the control of the vertical line relay 84. The fourth digit of the called numberv being 0 the subscriber presses the vertical button 8 ten times, as a result grounding the vertical conductor 11 ten times and operating the verticalline relay 44 and the'differential relay 46 of the repeater C ten times. The said line relay 44 in turn grounds the vertical trunk conductor 62 ten times, as a result causing the operation of the vertical line relay 84 of the connector F ten times. The current through the said verti ca'l line relay 84 flows through a circuit that has already been described. The vertical line relay in turn presses the lin relay springs 167 and 168 into contact, energizing each time the rotary magnet 87. The current flows through said rotary magnet over the followin circuit: from ground G through the, line relay springs 168 and 167 to the side switch wiper 93, thence through ther contact point 101, vertical magnet 87 and through the circuit-controlling relay springs 171, 172 and 173 to the battery lead 145, thence through battery B2 tov ground G2.

The rotary magnet 87 each time it is energized rotates the shaft and shaft Wipers 81, 82 and 83 one step at a time until they are carried` into enga ement with the normal conductors 175, 1 6 and 157l that lead to the first-selector E of the called line. The former two of said 176) do not terminate at the first-selector'E but continue through Ato the line conductors 177 and 178 of the called 'substation D. The subscriber again presses the rotary button 9 and grounds the rotary line 'conductor 12. e then operates the rotary line relay '45 of th'e repeater C (Fig. 1), grounds the rotary trunk conductor 63 and energizes the rotary line relay 85 (Fig. 2) of the connector F. he energization of the said relay 85 causes either of two results-the release of the side switch froin second to third position, if the called line is not busy, or the release ofthe 'connector-switch F, l busy, the former operation placing the side switchwipers 90 andl in engagement with the contact points 102 and 08, thus con- /nectiiig the calling subscribers line with the called subscribers line. e circuit over which thetwo substations are c0nnected, if the side switch passes to third position, is

Figs. 1 and 2.

ICO

conductors, and f 1,177,7ee v F? lt will be well to consider' tir-stthe former of said results, namely the release of the slde switch from second to third` position. The rotary .line relay 85. when it presses the springs 168 and 17 41 together, cnergizes the private magnet 88 over a circuit previously described. The said priva-te magnetoperatK ing momentarily releases the Side switch from second to third position. As a result the side switch Wipers llt and S11 engage the Contact points 102 and 1li- .so that the trunk conductors G2 and ('33 beti'een the exchanges #l and #2 are placed in connection with the subscribers vertical and rotary line conductors 177 and 178, respectively. At the saine time the side switch wiper Si* passes onto the grounded contact point -1 and a guarding potential is set up at the` private wiper 83 for protecting' the called ine after conne .ion has been established. The circuit for the establishment or" the guarding potential at the said private wiper extends from ground G1 to the contact. pointlO-l, side switch wiper 92, conductor 179 to the private wiper A guarding potential at the. said private Wiper 83, furtherinore sends a` flow of current through the bridge-cutoffrelay 180 of the first-selector lil, whereby the said relay when energized separates the springs 181, 182 and 188, as a result disconf nccting1r the Vertical and rotary line relays 181 and 185 from the battery lead 145 and from each other, so as to leave a talking and ringing circuit free. The current through said bridge-cut-od-relay 180 flows from the private Wiper 83 to the private normal conductor 157". thence through the switch shaft springs 186 and 187 to the bridge-entoilrelay 180, thence to battery lead 145 and through battery B2 to ground G2. To signal the' called subscriber the callingr subscriber presses his signaling button 7, pressing the spring 188 away froin'tlie contact point 189 and onto the ground contact point 190. The union of said springs 188 and 19 grounds the vertical line conductor' 11 over a circuit that extends from ground G3V through the groundsprings 119 and 120 to the spring 190, thence through the springl 188 to the vertical line conductor 11. As a result the vertical line relay 41 of the repeater C operates to ground the vertical trunk conductor 62 and` therefore, the vertical line relay 84 of the connector F is energized. lt will he borne in mind that non' the side switch is in third position and the side switch Wiper 83 ot the connector F is in engagement with the conw tact point 105: therefore when the vertical line relay presses the springs 187 and 168 into contact the ringer relay 11() is energized hy a flou7 of current from ground G to the side switch Wiper 93, thence through the ringer relay 110 and through circuitcontrolling relay springs 171. 142 and 178 to the battery lead 145, thence through battery B2 to ground G2. The ringer relay upon energizing shifts the springs 191 and 192 from the springs 193 and 191 and onto the springs 195 and 196. The result is that the calling line is separated from the called line and the ringer genere-tor 111 is bridged across the latter. A signaling current is, therefore. sent troni the ringer generator 111 to the subscribers line conductors 177 and 178, thence through the switch-hook 197 and Spring 198 and bell 199 to the rotary line conductor 178. Busy lines may bc either calling or called, and the Way in which protecting guarding potentials -re established has already been explained.

The calling line is protected by a guarding potential established at the connector banks from the calling first-selector, and. the called line is protected by a guarding potential established by the connector. ln

either case if the line is busy, therefore, there is a guarding potential at the private bank contact that corresponds to the called number. The busy release follows as a result of the energization of the rotary line relay for the last digit, ifthe called line is busy, as Vfollows: The said relay 85 upon eiiergizing energizes the private magnet 88, as 'already described, which latter in turn presses the springs 200 and 201 into contact. As soon as thc said springs '200 and .201 engage the release-magnet 89 is placed in connection with the private wiper 83 (since the side switch wiper 92 is now in second position and in engagement with theI contact point 10G)7 which latter has 'been previously routed onto a grounded Contact. As a result a flow of current is sent through the releasemagnet 89 from the'grounded private wiper 83 to the side switch wiper thence through the contact point 100, private springs 201 and 200 to the release-magnet 89, thence through theAcircuit-controlling relay springs 172 an l 17 3 to the battery lead 1115, thence througll battery B2 to ground GZ. The release-magnet npon energizing releases the connector switch Shaft and restores the connector side switch to first position, returning the vertical magnet 86 to the control of the. vertical line relay 84. Therefore it the calling subscriber (F ig. 1) presses his signalingT button 7 and grounds the vertical line conductor 11 he operates the connector vertical line relay 84, which latter in turn operates the vertical magnet Said vertical magnet raises the switchshaft so that the normal post arm 118 permits the switch shaft springs 117 and 116 to come into Contact and a. busy signaling current is sent to the calling snhscribers station. The circuit over which the busy signaling current passes is as follows: from the. coil 115 of the busy machine H through the Contact points 116 and .117 to the side rotary line rcluys .switch contact point 95, side switch wiper 91, ringer relay springs 1521 and 193, condenser 109, rotary line Wiper 147 of the seci-selector G, side switch Wiper 153, rot-runk conductor 6B, condenser 49 at specter C (Fig. 1), vertical line wiper 3 of the first-selector B, contact point 28, e switch Wiper 15, vertical line conductor 1i, receiver 2, secondary Winding 202 of the induction-coil 4, condenser 5 to the rotary conductor 12, thence through the side switch Wiper ,16 of the selector B, contact point 29, rotary line Wiper 34, condenser 50 of the repeater G,'vert1cal trunk conductor 62, side switch Wiper 143 of the second- L einer G (Fig. 2), contact point 158, verl line Wiper 146, vertical line relay 84 f e connector F, through the Windin of the differential relay 162 to the battery lead 145, and thence again to the coil 115- ci' tie busy machine H. The calling subscriber upon hearing the busy signal will widerstand that the desired line lousy and i release the switching apparatus by ig up his receiver. The front release 'hen culling subscriber restores ver 2 to switch-hook 6 and there rtf ection for a vnonncnt the f'. und 'Y :le sf" l e verticel M2 1,; 1.1 and 12 simultaneously, the cirenit from ground G3 to the vertical line conductor 11 being established through the ground springs 119 and 120 to the ground release-spring 204, thence through the release-spring 203 to the Vertical line coziaductor 11. The circuit to the rotary line conductor 12 extends from ground G3 to the :.'eleasespring 204, thence through 'i' releasespring 205 to the rotary line conr 12. its a result the vertical and 44 and 45 of the reguenter C energized over the usuel oircuits simultaneously. Said relays in turn ground the vertical and rotary trunk conductors and 63 simultaneously, the effect of which operation Will be considered presently. ,i ''The line relays 44 and 45 of the repeater also press the releasesprings 51 and'52 into contact, closing a release circuit through the backreleaserelay 35" off the irstselector B, and through the resistance-coil 48 of the repeater in series, The current for energizing the back-release-relay 35 flows from ground G at the first-selector B to the contact-point 30, thence to the side switch Wiper 19 and .through the hackreleaserelay 35 to the pri- 4rate Wiper 35, thence through the trunk release springs 51 and 52 and through the resistance-coil 48, pole changing relay springs and 61 to thegbettery lead 131, thence through cattery B1 to ground G1. W'hen the hackfreleaserelay 35" energizess, the

Larmes springs206 and 207 are then pressed inf/o contact and an energizing circuit is established through the release-magnet 37, current iowing from' ground G12 through the springs 206 and 207 to the said releasemagnet, thence to the battery lead 131 and through batter B1 to ground G1. The release-magnet 3 upon magnetizing attracts its armature and remains in readiness to release the switch as soon as the substation release-springs 203, 204and 205. separate and break the ground connection to the line conductors 11 and 12. e simultaneous grounding of the vertical and rotary trunk conductors 62 and 63 b the line rela s 44 and 45 of the repeater (l, (Fig. 1) resu ts in the energization of the vertical and rotary line relays 84 and 85, which latter press the trunk release springs 208 and 209 into contact and thereby energize the backreleaserelay of the second-selector G in 'series with the release-magnet 8 9 of the connector F, the current flowing .from ground G13 at the second-selector G to the Contact oint 161, side switch wiper 160, back-re easerelay 80, private Wiper 148, connector trunk release springs208 and 209 to the releasemuguet 89, thence through the said release magnet and through the circuit-controlling relay springs 172 and 173 to the battery lead 145, thence through hatte Bz/to ground G2. The release-magnet 89 of the connector F, as soon as' it energizcs, restores the switchshaft of the connector to normal positionl and the normal post arm 118 separates the 10a switch shaft springs 117 and 116, breaking the busy signaling current circuit.v The back-release-relay 80, like the back-release relay 35 of the first-selector B Fig. 1), energizes the release-magnet 77, which latter 10b is then put inreadiness to restore the said second-selector switch as soon as the subscribers release-springs 203, 204 and 205 Separate. All of these operationsresult as soon as the-subscribers release-springs 203, 204 and 205. come into contact; and as soon as the switch-hook 6 descends sufficiently to se arate the said release-springs,-the line relays 44 and 45 of the repeater C dener-l gize, ermitting the trunk release springs 51 an 52 to separateLthus destroyin the back release circuit that leads to the se ector B and through the back-release-relay .35', at which time the saidv selector B is fully restored. The dene'rgization of the rotary 126 line relays 44 and 45 removes the ground connection from the trunk conductors 62 'and-68, causing the denergization of the rotary and vertical line relays 84 and 85 of the connector F. When the said connector relays S4 and 85 denergize, the tn lk release springsv 208 and 209 separate and as a result the ehergizing circuit through the beck-release'relay 80 of the second-selector G and through the release-magnet 89 of the ne' mary winding of the induction-coil 4 to the rotary line conductor 12, thence through the side switch wiper 16 of the first-selector B and rotary line wiper 34 to the condenser 50 of the repeater C, vertical trunk conductor 6:2, side switch Wiper 143 of the second-selector G, line wiper 146, condenser 1084 ot' the connector F, ringer relay springs 194 and 192, side switch wiper 00, vertical line wiper S1, vertical line conductor 177, .springs 214 and 213 of the substation D. springs 217 and 218, transmitter 219, primary winding 220 to the rotary line conductor 178, thence to the rotary line Wiper 82 of the connector F, side switch wiper 91, ringer relay springs 191 and 193, condenser 109, rotary line Wiper 147 of the second-selector Gf, side switch Wiper 153, rotary trunh conductor 03, condenser 49 of the repeater C (Fig. 1), vertical line wiper 33 of the first-selector B, side switch wiper 13, vertical line conductor 11 and back to the transmitter 3. The voice-currents in said circuit are induced in the secondary windings 202 and 211 of the induction-coils 4 and 212, respectively, in connection with which coils are the receivers if. and i210. respectively. The front release after the called subscrilrer has answered may then be initiated by the calling subscriber in the usual mannerthat is, by hanging up his receiver and grounding the vertical and rotary line conductors simultaneously, but the circuits for energizing the release apparatus of the various switches are somewhat different from the circuits over which the front release occurs before the called subscriber' answers.

After the called subscriber has answered thesubscriber at station .'s. may restore the switches 'by hanging up his receiver 2 and pressing the release `prings 203, 204 and 205 together. grounding the vertical and rotary line conductors l1 and l2 simultaneously. as already described. Since the pole changing relay 47 is in an energized condition, grouniiling the vertical line conductor il snort-circuits the vertical line relay 44 and the winding 04 of the differential relay 40 between ground G and ground (is, and a result the current flowing through sa ndings ll and 64 is cut ofi' and the rela;` il is, therefore. denergized. The winding iof the differential relay 4G still maintains its llow oi' current from ground (la to the` battery lead 131 and to the battery Bl; theret'ore. the differential relay being thus unbalanced becomes magnetized, separating the spring 66 from the contact point 67, and causing in turn the deenergization ot' the pole changing relay 47 and of the line relays 84 and 85 ot' the connector F with which thc said pole changing reiajv i7 is connected in series. As soon as the pole. changing relay 47 denergizes,

Ation, which current however, the spring 58 leaves the spring 57, with which it has been in engagement, and returns to normal engagement with the ground spring 59, so that the ground connection to the ground spring allotted to the line relays 44 and 45 is restored. At the same time the spring 60 returns to normal engagement with the spring 01, so that the vertical line relay 44 becomes recnergized by a flow of current in the opposite direc-- now flows through the winding 64 of the differential relay 40 iu a direction to reinforce the magnetic effect oi' the winding 65. Both line relays 44 and 45 being now energized simultaneously, the ground connection being restablislied to the ground spring and the short-circuit being removed from the lmck-release-relay 35 of the first-selector B, the following results occur. The simultaneous grounding of the trunk line conductors (32 and 63. and the energization of the back-release-relay 35', over circuits that have been described. The backrelease-rel'ay 35', of course, energizes and in turn causes the energization ot the releasemagnet 37 of the first-selector B, which release-magnet now awaits the disengagement of the release-springs 203, 204 and 205 at the substation A in order to restore the selector B to normal position. The. simultaneous grounding of the trunk conductors 62 and 63 again energizes the line relays 84 and 85 of the connector F, with the result that the switch-shaft of the connector I" is released, the side switch is restored to normal position` and the baclr-release-relay of the second-selector is energized. These operations having already been described, and being well understood, it is not necessary to further describe them. As soon as the connector switch shaft returns to normal position the connection between the wipers 81, 82 and 83 and the trunk line that leads to the frst-selector E and to the line of the subscriber D is broken: therefore. the energizing circuits for the bridge-cutofi're lay 180 and for the pole changing and circuit-controlling relays 107 and 106 are destroyed with the result that the hist-selector E is restored to the control of the substation D, and the talking battery removed from the line of the called subscriber. All this occurs at the instant that the release-springs of the substation A come into Contact; but as soon as the release-springs separate. (a fterthe switchhook descends sutliciently) the switches are then fully restored to their normal position in the manner alreadv fully described.

The back release is provided in this system to enable the called. subscriber to destroy a connection that some other subscriber has made with his line in case the calling subscriber delays in restoring the switching apparatus. Were it not for such a provision the alled subscriber might once in a while llt) he inoonvenienoed h); not being able to make .1 will.. This alefl her, ily hanging ,111 his roceiwr 3H* grounding his linfconfine-tors l. l 'i siinul'faneously from sui 'ilim grammi (kin the usual naz ami over i1-mils si =1ilar to those i :n willi sahsiation A. ,zwilling relay l() inlay between short-circuit eX- :f1 aural il .hrouglfi the springs .".ii'al line. Conductor x11-e iirougli ,lf* rircuilcontrolling los.. (lillreniai relay springs 21.5 and .lo lf in the sul@ switfh Wiper 92 and to 151s the raid relay 106 l? and H3 come energizing eircuil wmgill/ isfuly desi i s i hcw' *en ih@ trunk release springs 20S he lin rela @l and S5 are imams@ he hanging relay bre. the eoni1 arrresfored. at utotirelay l@ of arial. the energizing Circuit ilarough the peil# @ringing relay l0? is broken al ille i1 121115.'. thaiv` the rotary line per Si! leaves engaging Contact. and the -raiease-relsiy l.) al die second-selectin (l enQrgif/.es in wies si .l1 he releaseauagnet fill and muse. lihe r ,use ui he seconab select-o1' (s in a wehflmmyn manner. Fur-- ther-nime, he energizing circuit for the pole rhangiug relay 4.7 of the repeat-er (l (Fig. l) is iestroffwl :1s soon the pole changing f lay lf?? the uonuector F' dener mes. sour. as ii" amara-files pilrws which it controls relu y 1.y anal as a result the lfm' nigh the transnii'mer 3 of uz all and the line relays regain huir normal condition. 11g al substation A, whenever 51e is rsa1 may evenually hang up his rereirer. wiiii lle resull that the sfvlevox' l raleus Yi sin? ihe trunk eondu nih .lf-:sn'icleil 11111111011-A "l in ."onnrction with the, vallei. subscriber '.llaneuus grounding of manifiestas and 43? (since the l i a :.ilseady released) 'he apparaus at; said office o fax r; rural rnirulifii'in.

ropes .er .ne i friius coils may he of any suilalfie res'f; uw., hut il. is found that resul. are olilaianal if he Coils if-il and e weh of one hundrel :mil fifty ohms,

Fil-0111 the foregoing' it will be seen that the repeater is o?? such character that it serres to Connect each side of a vulling leleA phone iin@ `ith the non- 3or1w spoznling side ol' the rallerl telephone line. lin other words. the Somalie@ vertical uonductor of the calling lim1 will he connectedwith the so-called rota ry coiulurior of the eallecl line, and the rotary Conductor of the calling line will he Conner-,ted with the vorlical conductor oi the ealled line. With this a1range1ueut the condenser in the yerlioal i (le of the trunk line circuit will not he subject io discharges as a result of Aimpulses transmitted over the vertical side of the calling suhscrihei"s line, and consequently the eondfrnsers thus employed will not tend to produce any confusion or uncertainty of action on the part ol the seooxnl-selecwr. nor on the part or the zonnector. The apparatus willv` of course. operate without haring the repeater line Conductors crrssul. hut with lhis creased arraruljeinent of the repeater line monili. dors, in coin hination with the common humeur arrange nient for supplying: i: lliing current ayer the lelephone lines io the suhsffriiiors lralisnit ters, .l limi that hurler results are obtained, and that the apparatus, particularly th second-senators and the connectors. will in the long run operate with more certainty of action. In other words, wih this crossed arranmalnrfiu of the line Comin/fio l in coinhiua'tion Willi the f1-0111111011 liaiery connections for talking purposes, lunch less delicate adjustniem is necessary for the line relays, particuhirly hosc of the selelztor and connector, in order to insure the proper operations. It will be understood. of course, 'that in any event the relays must all he properly adjusted, as hy suitably fensioning 'he springs of he rel y ar111alures, so as to insure the desired operations; but as stated and Ywilh'my improved arrangeinont, a delioate adjustment is possible1 particularly with respect to the line relays of the secondselectors and the connectors.

In the repeater I combine the crossed line eoruluctors with line relays for supplying talking current $0 the calling telephone line, and with a trunk release Circuit controlled hy said line relays; and in addition. l' prei4 @rably combine the crossed line conductors with a differential relay, whereby the trunk line circuit at one side of the cross therein is controlled by the normally closed conlasts of the said di'erential relay. Y@Vith this arrangement. the switch operating i111- pulses are eiliciently and accurately repeated froin one siile to the other of a cross in the the trunk line1 and at the saine time ille talking' current from the common talking' battery 1s efeetivvljr supphcd. to the circuit.

or other suitable switch, in the direction of the calling subscriber. In this way three trunk conductors may be employed between the first-selector and the repeater, and between the second-selector and the connector, while only two crossed trunk conductors are employed between the repeater and the, second-selector. As explained, the batteries which supply current for operating the selectors and connectors, or other suitable switching machines, as well as the repeaters, are also employed for supplying electrical current over the telephone lines to charge the microphone transmitters connecting the lines at the subscribers substations. Preferably, for the purpose of trunking between two distant exchanges, one battery is employed for supplying current through the repeater to the callingl telephone line, and another battery is then employed for supplying current through the connector' to the called telephone line-that is to say, when the two lines are located at di erent exchanges. It will be understood, of course, that a subscriber of one exchange may call a subscriber of the same exchange without using a repeater, and by the use of threeconductor trunks throughout the connection between the callingl and called lines. For trunking between exchanges, however, only two crossed conductors are employed for each trunk line.

In Fig. 3 it will be seen that the line con ductors of the repeater are crossed in front of the condensers 49 and 50, rather than back of the condenser-s, which latter is the case in Fig. l. In Fig. 3. however, the upper' condenser l!) is.connected temporarily,` that is, during the establishment of a connection-of course, with the rotary side of the calling subscribei"s telephone line` while Athe condenser 50 is connected also temporarily, of course, with the vertical side of the calling subscribers line. With this arrangement the vertical trunk conductor 62 runs directly from the condenser 49, while the rotary trunk conductor F3 extends directly from the condenser 50, the cross in the circuit being located between the condensers and the bridge of the line relays 44 and 45. For the broader purposes of my invention the line conductors of the repeater may be crossed either in front or in rear of the condensers. lVith either arrangement any kick through a condenser from the "ertical side of the calling subscribers line will be communicated to the rotary side of the trunk line, thus precluding any confusion or uncertainty7 in the action of the second-selector, or of the connector, as the case may be; and in a similar way any kick through a condenser from the rotary side of the calling subscribers line will be communicated to the vertical side of the trunk line. At the same time an eflicient talking circuit is provided, the crc' the line conductors at the repeaterI im@ of course, no detrimental effect on the 1a currents. With either arrangemerr two crossed trunk conductors are o.. between a repeater and the seconde and at the same time threeeendu may be employed between the in and the repeater, weil as bete. Y. second-selector and the connector. wWhat l claim as my inventicei l. ln a telephone excha combination of a line circuit AVlaying crossed conductors, a pair of line relays bridged across the circuit at one :side at' the cross therein, inductive, conn=;-itions in the circuit at the other side of said cross, an automali" switch in the circuit, unam` lli' which the calling subscriber uses said relays for wir trolling said switch. and .means for supplw ing talking current through the windii fs of said relays to the calling end` of sarl circuit.

2. In a telephone exchange combination of a line circuit ha line conductors. an automatic nected in the therein, a pair ol iclays bridged :fici'oss the circuit at the other side ofy said cross. means by which the callingv subscriber -eniployssaid relays for contr lling said automatic switch, and means tor supplying talking current through the wiinlni s of :said relays rfi the calling end of said circuit, and through thc said automatic switch to the called 1n-@l it said circuit.

3. In a telephone exchange srstcni. ille combination of a calling telephone lila'. a called telephone line. a treuil: line ciinnection temperarily connecting the tivo telephone lines together, said trunkY line connertion comprising a pair ol crossed liz. riaiilurtors, whereby the iso-called vertical '-onaluctor of one telephone line is connected with ihe socalled rotary conductor oi the other tel-r--- phone line, a connectlireu itch by which the trunk connection is established directly with the called telephone line, a pair ot' relays bridged across the trunk line connection at a point between the calling telephone line and the said crossed line conductors, a bat-l tery for supplying current through the u indings of said relays to the calling telephone ein, the

switch c circuit at one side of the cri ...s

line for talking puri'ioses, another battery for supplying current through the said von Wil lill@ linx: cimnit l ming Tossed comiwf'mr-l` n pun' nl lizw relays bridged :nxnsf: tlw i'iivnil, at` mw Filhe nl' the vloss thei'iin, inlnviw Wnnf-linnwl in lln ii-cnil nt thc Ulhil :ills nl' :mill Nimm un :nllnnmth switch in thv vn'vnil. .will ,"wilvh having um. nmtion ln :wlw'l gnnnp unil nnnthm motion to unxianw't with :l lrns in zinj" group silcvtcd hy the lix'bfl motn-n, nimns` hy whii'li the v; lling snhsvl'ihvi' nbw will inlays lm' mntmllinz;r anni `ill-h. :unl mmm; loi' supplying talking; mn'i'vnt. tln'nngh tlm windings of said i'sflnys in the milling cnil nl' szliil circuitA Vln n [nh-phone vxifhzingn sybnl'mn, thv wnibinntinn nl a lino viicnii having m'nebcll linc Qnmfllnlm's, un :inlnnmtiif #wit-h mnnmlfsxl in llw 'ixciii nl nini ahh nl the wss llwi'cin, unl :Minh having mn nmlinn lo wlmi ginllpr, :unl unulhcr nmtinn tu connect with :i line n :my group svlu'l'wl hy lln` lint molinrn 1i infn' hi'imlgcil :www lhs circuit :il thv ilflici nialv nl' Mnl cross* nwnns by Whivh the falling snhml'ihcl' nniplnys miil i'iluyS lm' controlling mill linlonmtiv swilch, anni nnb-m15 for Snp'flyngf talking vinficnt lln'oinfli the windings, nl' nhl wlnyh' tu ihn i. L; enfl nl xml lvire-nil', anni lhiunggh thu anni milninfiic witch tu lln: l'nllcll cnil of will circuit.

Signed ny nw :it lfhivzigo, (funk illinois, thi` lllh luy nl July, 1006,

TA LBOT l. MA RTN.

County. 

